Stroboscopic apparatus



Aug. 23, 1938. A, HE ETAL 2,127,605

S TROBOSCOP I C APPARATUS Filed May'29, 1935 3 She ets-Sheet 1 IIIIIIIIIA "'41," W M' l l\\ I Aug. 23, 1938- A. A. KUCHER ET AL STROBOSCOPICAPPARATUS Filed May 29, 1935 3 Sheets-Sheet 2 Aug. 23', 1938.- A K gER'2,127,605

STROBOSCOPIC APPARATUS Filed May 29, 1935 3 Sheets-Sheet 3 2993942 III!Patented Aug. 23, 1938 UNITED STATES PATENT OFFICE srnonoscorroaPPAnA'rUs Andrew A. Kucher and Floyd E. Gray,

Dayton, Ohio Application May 29, 1935, Serial No. 24,058

' 3 Claims.

accurate in operation andrelatively inexpensiveto manufacture.

A further object of our invention is to provide a stroboscope for theinspection of rapidly moving elements in which the element may beinspected during periods of acceleration or at various constant speeds.

A still further object of our invention is toindicate the frequency ofthe periodic motion of the element under observation.

It is a further object of our invention to provide apparatus of thischaracter which is portable and which may be readily set up foroperation.

These and other objects are effected by my invention as will be apparentfrom the following description and claims taken in connection with theaccompanying drawings, forming a part of this application, in which:

Fig. 1 is a'perspective view of a stroboscope constructed in accordancewith our invention;

Fig. 2 is a wiring diagram of the apparatus shown in Fig. 1; v

Fig. 3 is a sectional view of a tachometer mechanism and is taken inline III-III of Fig. 4;

Fig. 4 is a sectional view taken along line IV-IV of Fig. 3;

Figs. 5,. 6, and '7 are diagrams of various connections of some of theelements of Fig. 2;

Fig. 81s a sectional view of amodifled form of our improved apparatus;and

Fig. 9 is a wiring diagram of the form of apparatus shown in Fig. 8.

.The operation of stroboscopic apparatus of the type disclosed herein isgenerally known in the art, but, briefly stated, it consists inintermittent- ,ly illuminating a rapidly moving elementat a frequencycoinciding with the frequency of the periodic motion of the movingelement whereby an 11- lusiozr is presented in which the element appearsto be stationary. Therefore, the element may be viewed and studiedduring operation.

Stroboscopes in the past have been bulky, heavy and inconvenient tooperate, especially where the element to be observed is so located thatits illumination is diflicult. We have obviated these diiiiculties byproviding a light, portable in- 50 strument which may be easily set upfor operation. We have, furthermore devised a stroboscope with -atachometer attachment whereby studies of moving elements may be made.Indications of the frequency of the periodic motion of the element underobservation are provided by ourimproved device, both during accelerationand at times when the frequency of the. element is constant. Adescriptionof the construction and operation of our improved stroboscopewill now be made.

Referring now, particularly, to Figs. 1 to 6, in-

, clusive, the apparatus is shown arranged within a portable carryingcase having a section III which encloses various control and powerinstrumentalities and a lid I l which houses the illuminating device l2,for example, a gas filled electric discharge lamp. A reflector I2A maybe disposed in the lid ll behind the lamp l2. For flexibility inoperation, the lid II is detachable from the control section III,whereby it may be arranged for illuminating the element underobservation at a point remote from the control section It).Disconnecting type hinges l3 may be employed for this purpose and aflexible-cable l4 may be employed for electrically connecting theilluminating device l2 to the power apparatus within the section Ill.The carrying case may also include a lock l5 and a carrying handle I6.

The control and power instruments arranged within section ID of thecarrying case are shown in Fig. 2 and will now be described. Alternatingcurrent is supplied for the operation of the stroboscope by means ofconductors l1 and I8 con- ,nected to'a detachable plug I9, and a mainswitch 2i is provided in the conductor 18 for controlling theenergization of all of the apparatus. Other major elements of the powerand control apparatus contained within the section I 0 are a motordriven switch mechanism, generally indicated at 22, a rectifier 23, arheostat 24 for controlling the speed of the motor driven switchmechanism 22, a multi-position switch 25 for a purposeto be referred tohereinafter, astep-up transformer 28 for providing a relatively highvoltage for the electric discharge lamp l2, a jack 2'! to be describedhere-. inafter and an indicating instrument 28. Switches 2| and 25andthe rheostat 24 are, respectively, provided with operating handles2IA, 25A and 24A,.shown in Fig. l. A panel 29 is fixed in the section l0and carries indicia, as shown, for indicating the positions of theswitches 2| and 2B and the rheostat 24.

The motor driven switch mechanism 22 is em ployed for controlling theenergization of the lamp l2 and includes a small motor 3| having anenergization winding 32 and a rotatable shaft 33. Various types ofmotors may be employed, but I prefer to use a small, variable speed,alternatingcurrent motor operating at a commercial voltage andfrequency. The switch mechanism includes a small rotatable contact 84insulated from and 1'0- winding 32 of the motorhas one of its terminalsoutput leads til and tated by the motor shaft 33. Qooperating with therotating contact it are a plurality of brmhes till to 38, inclusive,which are insulated from each other and which are so disposed thatadjacent brushes may be bridged by the rotating contact S6. The

connected to the line conductor it and the oppo site terminal of thewinding 32 is connected to the other line conductor it by a circuitincluding a conductor til, rheostat 2 3, a conductor 3 t. and the switchit.

Direct current is employed for energizing the lamp it because of theflicker present with the use of alternating current on a gas filledelectric discharge lamp. Direct current is obtained by the use of therectifier which is shown by way of example as a full wave rectifierhaving a rectifying tube t2 and a transformer it. The primary M of thetransformer is connected to the alternating current line conductors i land it and is controlled by the switch 2i. The secondary oi thetransformer it includes first and second wind lugs t5 and it,respectively; the winding 45 being connected to the plates of the fullwave rectifier tube 62 and the winding 35 furnishing the filamentcurrent. Other elements of the rectifier include the usual resistor iand condenser 416 which are connected across the direct current As theoperation of full wave rectifier-s is well-known in the art. no furtherdescription of them is deemed necessary.

. Enereization of the lamp it is efiected from the direct current leadsit and iii in a manner to'be hereinafter described. The energizingcircuit includes the transformer 26 which has a primary winding 52 and asecondary winding i553 connected to the terminals oi the lamp it? bymeans of the flexible cable l6. Electrically connected in the circuitoi. the primary winding is the meter 28, which responds to andpreferably indicates the frequency of energization of the circuit. Whileother types of meters may be employed, we prefer to use a dampenedammeter calibrated in the manner set forth. The meter 28 may be arrangedin the case iii (Fig. l.) where it will be readily available for readingas the various control handles are adjusted dining on oration.

As pointed out in detail hereinafter, the rotat ing switch tit isconnected in the direct current circuit for controlling the eneraisationof the transformer 26 and the lamp l2. llhe multi-posltion switch 25 isinserted in this circuit and is connected to the brushes 3b to 88,inclusive, for changing the connections thereto, whereby the number orenergizations of the lamp 82 per revolution or the switch 538, may bevaried as the switch 25 is moved from one position to another. With thisarrangement a greater range of operation may be obtained than isafforded by the speed range or the motor ell. For example, assmile thehigh speed of the motor Si is 3M0 R. P. M. and that the lamp isenergized once per revolution, then the highest speed of the elementarsacos The contact 55 is connected to the direct current lead m'bymeans of a conductor H and a pair of closed contacts" and 13 of the Jack2?. Contact 63 is connected to the prlmm E2 oi the transformer 26 bymeans of a conductor it. The contacts (it, 97, t9 and (it areelectrically connected as shown to the brushes til, 30, ill, and so,respectively.

In the first position of the'switch 25, segment (ii bridges contacts 55and 58, and the segment t2 bridges contacts El and 68. For the rotatingcontact 84! momentarily engages brushes 5 86, the primary 52 of thetransformer E6 is ergized through a circuit including direct currentlead 419, contacts 72 and it, conductor ll, contact 56, segment 6i,contact lid, brush ro toting contact 36, brush 3. contact ill, segmentE52, contact 58, conductor it. primary [32, meter 2t] and the oppositedirect current lead iii. A high voltage is induced momentarily in thesecondary which causes an electrical discharge in the filled lamp l2 andefiects illumination. in this. position of the switch 25, the brushestit and t ment (it bridges contacts 68, Mi, and ill, and the segment onconnects contacts EB, lit, and G6? The efiect of these connections isshown in 6 from which it will be apparent that the circuit includingconductors ii and i l is energized twice per revolution, 1. e., when therotating contact at bridges brushes 3?: and I8 and when it bridgesbrushes 3t and 3'1. Therefore, the lamp i2 is;

illuminated twice per revolution of the motor ill or once for everydegrees of travel of the contact 2%.

In the remaining position of the switch, indlcated as number 6, contactsElli, b6, and G9 are connected by segments 65 and O'l, the letter beingelectrically connected together. Likewise. the connected segments (56and 68 engage the con.- tacts 5?, B8, and 6b. The silent oi theseconnections-is shown in Fig. '7 from which it will be seen that thecircuit including conductors ii and, it is energized four times perrevolution of the contact 35 or, in other words, once every Bil degreesof travel of thecontact St. The lamp ii? is illuminated, therefore, fourtimes per revolution oi the motor 8 I. I

Operation When a study of arapidly rotating element is to be made, thelamp I2 is arranged to illuminate the same. 4 operation of the motor 3|and the rectifier 23. The switch 26 is adjusted to the proper settingdependent-upon the speed of the element to be observed.

AdJustment of the speed oi the motor my a The switch 2| is closed forinitiating M is made by moving the handle 24A of the rheostat 24 untilthe element under observation appears to be stationary. As mentionedheretofore, this will occur when the frequency 01 lllumination by thelamp l2 coincides with the Ire- 2,127,805 I V J quency of revolutions ofthe element. A-physical study of the element at high speed may then bemade and any defects in the element, flexing thereof under load or otheroperating'characteristics may be observed. -By referring to the meter29, the exact speed of the element may be noted, which speed is theequivalent of the frequency of illumination indicated by the meter.

The description of operation in the foregoing referred to a rotatingelement but it will be understood that studies of reciprocating oroscillating elements may be made as easily as are those of rotatingelements. Furthermore, the frequency of the -periodic motion of theelement being studied will be indicated by the meter 28 when theillusion of a stationary element is obtained.

In order that a rotating element under observation may be viewed duringperiods of acceleration, we provide a tachometer-drive mechanism l5,shown in Figs. 3 and 4, which includes friction cone 15A carried by aspindle I9. The cone 15A may be held in engagement with the usual lathecenter in the end of the shaft of the element so that the rotatingspindle E6 of the mechanism 15 is rotated in synchronism with the shaftof the element. A switch contact "ill is rotated by the spindle l9 andbridges stationary brushes 19 and 19 during each revolution. The brushesl8 and 19 are connected by conductors 8i and 82, Fig. 2, to contacts 83and 94, respectively, of a plug 85. The latter is inserted in the jack2! at times when the tachometer-drive mechanism is to be used. The jack21 includes, in addition to the normally closed contact 12 and i3, acontact 89 which is engaged by the contact 94 when the plug 95 isinserted in the jack 21. At this time the plug contact 83 engagescontact 12 and the con-. tact l9 bears against an insulated portion ofthe plug 85 and, therefore, the circuit including the conductors H and19 is open Accordingly, the

rotating switch driven by motor Si is ineffective to control theenerglzation of the lamp 12 due to the open circuit at contact I9.

During operation'of the stroboscope with the tachometer-drive mechanism1.5, the motor 3| may be stopped by adjusting the rheostat 29 to its offposition. The switch 2| remains closed, however, for energizing therectifier 29. The illumination of the lamp i2 is under control of therotat- I ing switch contact ll of the tachometer drive mechanism 15. Thecontrolling circuit may be traced from the direct current lead 49 of therectifier 23, Jack contact 12, contact 89, conductor 9!, brush it,rotating contact I1, brush l9, conductor 82, contacts 94 and 99,conductor 14,-transformer primary 52, meter 29 and the opposite directcurrent lead iii of the rectifier 28.

The lamp i2 is illuminated at a frequency equivalent to the frequency ofrotation of the shaft of the element under observation. It will beapparent that the frequency of illumination increases directly with anincrease in frequency of rotation of the element being observed..Therefore, the illusion of a stationary element is obtained throughoutthe period of acceleration and prior embodiment. Themotor 9| has ashaift 99 which drives the rotating switch contact 34 and an indicatingneedle 9| of the tachometer by means of a magnetic induction connectiongenerally indicated at 92. As connections of this kind are well-known,it is not deemed necessary to describe their construction or operation.It will suffice to say that the faster'the motor shaft 99 is rotated,the farther the needle 9| is advanced so that. the speed of the motormay be read on a scale which we show at 93. The scale 93 is preferablycarried by the panel 29 and a transparent shield 94 is arranged abovethe scale 93 and needle ill for protective purposes.

Arranged at the bottom of the shaft 99 is 'a connection for coupling atachometer thereto for driving the shaft 99 and the indicating needle 9|when the tachometer is to be used. The coupling 1 may be provided in anydesired manner as, by a square socket 95 arranged in the motor shaft 99and a rotatable square shaft 96'forming a part of a tachometermechanism, generally indicated at 911. The tachometer-drive 91 includesthe usual friction cone 98 which drives the shaft 96 bymeans of aflexible shaft mechanism shown at 99. A fitting l9l may be provided forattachment to a fixed bushing I92 in the case l9, when the square shaft96 is inserted in the socket 95 of the motor cept that the jack 21 andthe meter 29 have been omitted. The other elements of the control andpower apparatus are similar to those of the prior embodiment and aresimilarly connected. For purposes of description, the elements which arecommon to both embodiments are designated by like numerals. g

When operating the stroboscope disclosed in Figs. .8 and 9, the mainswitch 2| is closed for energizing the rectifier 29 and motor 3|. Therheostat 24 .is adjusted, until the desired speed of the motor 3i isobtained. At this speed, the lamp i2 will'be energized by the rotatingswitch contact 29 as it passes over the brushes 35 to v98, inclusive,and the moving element being studied will appear stationary; all ofwhich has been previously described.

Thespeed of the observed element may be obtained by referring to theneedle 9i and scale 93. In this connection, the speed indicated by theneedle 9| can be directly taken as that of the elefor each revolution ofthe motor shaft 99. With the switch 25 inits second position, thebrushes will be connected as shown in Fig. 6 and the lamp i2 will beilluminated twice for each rotation of the motor shaft 99. Therefore,the speed of the element being observed must be twice the speed of themotor 9! and the indication bythe needle 9i shouid'be multiplied by twoin order to obtain the correct speed of the observed element. Likewise,a multiplier of four is used to obtain the correct speed of the"observed element if the switch 25 is in its number four position, orthe position in which 'the'lamp is illuminated four times for eachrevolution of the motor shaft 99.

With the tachometer drive .91 connected to the motor shaft to, the motorii is deenergized, for example, by adjusting the rheostat 24 to open thecircuit of the motor winding 32. switch it, however, is closedforenergizing the rectifier 23. The tachometer drive 9! drives therotating switch contmt M and the speed indicating needle 9i. llhefrequency of illumination of the lamp it is in synchrony with thefrequency oi rotation oi the observed element which appears stationary.The speed can be read directly from the position of the needle 9! as theswitch. 25 should be in its first or number one position for operationwith the tachometer-driving device 97?.

While we have disclosed our improved strob-oscopic apparatus embodyinga. gas-filled electric discharge lamp, it is to be understood that otherforms of lampsmsy be employed which rapidly illuminate upon applicationof a suitable poten-- tial thereto and which darken instantly with theremoval of the potential. Furthermore, we have shown a hill Waverectifier of the type employing an electric discharge tube but it is tobe understood that other iorms of rectifying devices may be used.

While we have shown our invention in two forms, it will be obvious tothose skilled in the art that it is not so limited, but is susceptibleof various other changes and modifications without departing from thespirit thereof, and we desire, therefore, that only such limitationsshall be placed thereupon as are imposed by the prior art or as arespecifically set forth in the appended claims. 7

What we-clsim is:

i. In apparatus for inspecting a moving element and for indicating thefrequency of the periodic motion thereof, the combination oi anelectrical circuit, means for illuminating said element connected insaid circuit, a rotatable switch structure having a plurality ofclrcunrferentlally Y spaced stationary contacts and a rotatable memherfor sequentially bridging adjacent stationary contacts as it is rotated,said rotatable switch being connected in said circuit with saidilluminating means for controlling the energization thereof. a motor forrotating the br'idging member, a second switch structure having aplurality oflstationary contacts connected, respectively, to thestaionary contacts of the rotatable switch structure and otherstationary contacts connected in the electrical circuit, saidsecond-switch structure having an element selectively movable to aplurality of positions. said element including segments adapted forbridging predetermined The main issect groups of the stationary contactsin the diflerent positions of the element, the connections between thestationary contacts of the first mentioned switch structure and the saidpredetermined groups of contacts of the second switch structure being soarranged that different predetermined groups or said first mentionecontacts are connected in the circuit in the di ere'nt positions of themovable element so that the number of energizations ofthe illuminatingmeans per revolution of the motor is varied, means for varying the speedof said motor and means responsive to the speed of the motor forindicating the frequency of energlzation of the illuminating means.

'2. In apparatus for inspecting a. rapidly mcv ling element and forindicating the frequency of the periodic motion thereof, the combinationoi an electrical circuit, means for illuminating said element connectedin said circuit, a rotatable switch structure having a plurality ofcircumferentially spaced stationary contacts connected in saidelectrical circuit with said illuminating means for controlling theenergization thereof and having a rotatable member for sequentiallybridging adjacent stationary contacts as it is rotated, a motor having adrive shaft connected to the bridging member, means for controlling theenergization of the motor and for adjusting the speed of said motor,means for indicating the speed of the drive shaft of the motor, a devicefor connection to the element under observation and rotatable insynchrony with the periodic movement of the element, and means forreadily connecting said device to the motor drive shaft for motivatingthe same so that the frequency of the periodic motion of the element isindicated by the indicating means.

3. In a portable stroboscope. the combination of a carrying case havinga detachable cover, an electric discharge lamp arranged within saidcover, rectifying means disposed within said carrying case and includinga direct current output circuit for energizing said lamp, 9. source ofalternating current for energizing said, rectifying means, a flexiblecable connecting said direct current circuit to said lamp so that thelamp may be arranged remote from said case during operation,

means connected in said direct current circuit for intermittentlyenergizing the same and disposed in said carrying case. means arrangedin said case for varying the frequency of operation of the energizingmeans, and means carried by said case for indicating the frequency ofenerglzation of the energizing means.

ANDREW A. KUCHER. FLOYD E. GRAY.

